When my users log into SiteStudio from H-Sphere they get SiteStudio login page...

Resolution

Make sure, that the variables MASONRY_URL in the /hsphere/shared/SiteStudio/psoft_config/masonry.properties file and PATH_SITE_STUDIO in the /hsphere/local/home/cpanel/shiva/psoft_config/hsphere.properties file are set to the same URL.